turbulent pipe flow

August 2, 2005, 04:44

How do i calculate boundary conditions for turbulence at the inlet and outlets? I have the reynolds numbers at these boundaries, and the diameters for the pipes.

Reading the user guide, I am assuming i use the turbulence intensity and length scale to define the turbuence. Does anyone have some good approximating formula's for these parameters?

My model involves a compressible gas flow at 6000kPa (within a natural gas transmission pipeline).

Thanks.

August 2, 2005, 10:52

Intensity (Refer Fluent manual for calculating turbulence intensity -> http://www.fluentusers.com/fluent/do...e180.htm#26619) and Hydraulic diameter (= diameter of pipe for a cylinder even if modeled in 2D).

August 2, 2005, 13:00

it is difficult to calculate them accurately. a thumb rule says that moderate intensity of 5% should be used. at the upper range, it can be 15-20%. i am not sure about length scale range.

Swarup.

August 2, 2005, 04:44	turbulent pipe flow	#1
John Guest Posts: n/a	How do i calculate boundary conditions for turbulence at the inlet and outlets? I have the reynolds numbers at these boundaries, and the diameters for the pipes. Reading the user guide, I am assuming i use the turbulence intensity and length scale to define the turbuence. Does anyone have some good approximating formula's for these parameters? My model involves a compressible gas flow at 6000kPa (within a natural gas transmission pipeline). Thanks.

August 2, 2005, 13:00	Re: turbulent pipe flow	#3
Swarup Guest Posts: n/a	it is difficult to calculate them accurately. a thumb rule says that moderate intensity of 5% should be used. at the upper range, it can be 15-20%. i am not sure about length scale range. Swarup.

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August 2, 2005, 10:52	Re: turbulent pipe flow	#2
pUl\| Guest Posts: n/a	Intensity (Refer Fluent manual for calculating turbulence intensity -> http://www.fluentusers.com/fluent/do...e180.htm#26619) and Hydraulic diameter (= diameter of pipe for a cylinder even if modeled in 2D).